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| Total’s CLOV FPSO is an example of the shift toward integrated classification, certification, and lifetime asset integrity maintenance. |
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CLOV is the fourth major project, which Total and its partners have developed in the prolific Block 17 in deepwater Angola. CLOV follows previous projects—Girassol, Dalia and Pazflor—and builds on all the experience with these projects. To ensure reliability of the complex project, Total used Bureau Veritas (BV) as a single entity to perform classification of the floater, and certification of the topsides, risers and subsea installation.
CLOV PROJECT BACKGROUND
Block 17 is operated by Total on behalf of the concessionaire, Sonangol, with partners Statoil, Esso and BP. The CLOV FPSO is 140 km from Luanda, in water depths ranging from 1,100 m to 1,400 m, bringing onstream four fields: Cravo, Lirio, Orquidea and Violeta.
Built by South Korea’s Daewoo Shipbuilding Marine and Engineering (DSME), Total is now completing the CLOV installation, hook-up and commissioning phase. The FPSO will begin production in second-quarter 2014 and build up production to a plateau of 160,00 bopd. The floater is 305 m long, 61 m wide, and has a storage capacity of about 1.78 MMbbl.
CLOV DESIGN & CONSTRUCTION
The CLOV project consists of a total of 34 subsea wells, eight manifolds and one multiphase pump system, 38 km of production lines, 57 km of water injection lines, 84 km of umbilical, 32 km of gas export lines, two hybrid riser towers, and a single hybrid riser for the gas export. This installation is being tied back to the FPSO.
Innovations on CLOV FPSO include two water treatment systems, with ultra-filtration, and Minox system, with an injection capacity of 319,000 bpd. Gas for export can be compressed at the rate of 65,000 cmd. CLOV has all-electric variable-frequency drives, powered by 3+1, 28-MW GE aero-derivative turbo-generators.
FPSO construction. The FPSO has steel construction, with a double-sided hull and single bottom. It is held on site with a spread of 16 mooring lines. The topsides run a commingled (Oligocene and Miocene oil), single-train process (wash-tanks and settling tanks in hull), and storage. The topsides dry weight is about 31,000 t, and there are 12 modules, with space for expansion. The liquid treatment capacity is 229,200 bopd.
Multi-phase subsea pumping. Through a unique, dual-phase processing and storage system, the CLOV FPSO will produce two types of oil: one with a 32°–35° API gravity from the Oligocene reservoirs (Cravo-Lirio) and the other, more viscous, with a 20°–30° API gravity from the Miocene reservoirs (Orquidea-Violeta).
This feat will be accomplished through a deepwater helico-axial, multi-phase pump system. At a 1,170-m water depth, the powerful pump system will optimize recovery of hydrocarbons from Orquidea and Violeta fields, two of the four reservoirs, where the oil is more viscous and pressure conditions are less favorable. The technique will ensure that production can be maintained through three years of operation. The pump can tolerate fluids made up of oil, gas and water, without separation. Two such pumps are installed, one in reserve. Independent checking of the design, fabrication and installation of subsea pumps of this nature is fundamental, to ensure field production reliability.
Flaring technology. There is no routine flaring from the FPSO. Many projects have a no-routine-flaring policy, but leave a pilot flare lit, so that, in the event of a safety incident or process upset, the full flare can be ignited very quickly. The pilot flares stay lit all the time. The flares are fed by a small supply of gas, but that supply has to be strong enough to ensure that the wind doesn’t extinguish the flare, and that there is no air ingress in the flare stack.
If a pilot is not used, another failsafe method is required for immediately igniting the flare. CLOV uses a pelleted ignition system. When gas is vented to the flare, an incendiary pellet is shot at the flare tip, using compressed nitrogen in a guide tube. Having no pilot flare will help reduce CLOV’s greenhouse gas (GHG) emissions, compared to an FPSO with a conventional pilot flare.
The CLOV development scheme is, itself, a GHG-reduction tool, because associated gas within the process is recovered, compressed and exported to an onshore liquefaction plant. The fact that an export pipeline exists is an added incentive for having a true, no-flaring policy.
Extensive local content. What distinguishes the CLOV project from its forerunners is the considerable increase in local content. In all, there have been more than 9 million hr of work and 64,000 t of fabrication and assembly achieved in Angola. For the first time, a full module—the water treatment module—has been built, installed and integrated on the FPSO at an in-country yard.
RELIABILITY ASSURANCE
A key issue for the CLOV project has been reliability assurance. “Working in water depths to 1,400 m means that to remove and replace any item is a huge task with HSE and quality issues, and has a huge impact on production,” explained Geneviève Mouillerat, project director for Total E&P. “So, it is absolutely fundamental that the equipment does not fail, and installation is done right the first time. The equipment put in place has to be of the highest quality, and there have to be continuous checks to ensure that this is the case.”
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| Geneviève Mouillerat, project director for Total E&P. |
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Mouillerat further elaborated that when Total is looking for a supplier or contractor, the company wants three key things. “Reliability, reactivity and transparency are what matter to me, and to Total,” Mouillerat said. “Transparency is most important. We must have trust in the relationship. Nothing is ever perfect, but if things are out in the open, they can be dealt with, so transparency and trust are key values.”
Total used BV to class the CLOV FPSO and unloading buoy, and certify the main equipment on the FPSO, together with the subsea installation, all the moorings, risers and flowlines, Fig. 1. “We have done it all with one certifying body, and it gives us continuity across the project,” says Mouillerat. “We began the certifying process right at the design stage and worked with BV step-by-step, so that they can verify the project from design to construction through commissioning and first oil.”
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| Fig. 1. CLOV topsides. The topsides dry weight is about 31,000 t and has 12 modules, with space for expansion. |
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According to Mouillerat, the benefits of working with BV are three-fold. “First, we know each other and have a good working relationship, which helps. Second, they are a reliable company, whom we know we can trust. Finally, and most importantly, they are, and they stay, fully independent. They have their own view and maintain their independence as they control each step we take,” Mouillerat said. “At the end, a truly independent control is the most important benefit we get.”
CLASS & CERTIFICATION PROCESS
Since the beginning of the CLOV design review in 2010, BV has deployed engineers and inspectors in Korea, Angola and Europe, to perform continual checks on the FPSO equipment and construction.
Contract scope. The class and certification contract with BV included project management, design review, construction survey and commissioning, anchors and mooring lines installation, and FPSO hook-up. Additionally, the contract covered an offshore tow of 75 days, plus commissioning and certification of subsea umbilical, risers and flowlines (SURF), and 2nd-party equipment inspections. The standards that the equipment had to meet were set by Total itself, based on previous experience, as expressed in their project specifications.
Standards. The standards for the construction and testing of the FPSO hull were set by BV class rules, under normal classification requirements, for offshore floating units built in steel. BV has extensive experience with offshore floating structures, and special fatigue issues, which FPSOs have to withstand. Extensive hydro-structure research underpins the experience. BV has worked on almost half of all the FPSOs in the world to date, either to class them or to provide studies for the operators. That experience is built into the continually updated classification rules, which ensure that the structure is correctly dimensioned and built, so that it can perform for the design life on station, without need for taking it out of production for repairs.
Riser standards are set by API, and BV works to those specifications. Standards for the moorings and offshore unloading buoy are written into BV offshore rules and build on its experience with offshore floating units. BV’s Ariane software suite was used to analyze the moorings and validate them.
Integrated process. Total’s CLOV FPSO is an example of the shift toward integrated classification, certification, and lifetime asset integrity maintenance. Korea’s DSME and Total entrusted structural integrity management tasks for the CLOV FPSO to BV’s consultancy arm, Tecnitas. Together, the teams produced a structural integrity program, including a Design, Fabrication and Installation (DFI) Resumé and finite element analysis, using a complete model of the hull and topsides in as-built condition.
The purpose of the DFI Resumé is to identify structural areas, where critical problems are encountered, and how they can be solved during the design, fabrication and installation phases. This includes descriptions of the most relevant shipyard non-conformities and corresponding corrective actions. The DFI Resumé is then used as the basis for inspection and maintenance plans.
Having a validated finite element model (FEM) of the whole vessel in as-built condition is particularly important, because it reflects the condition of the FPSO at delivery stage, Fig. 2. This model can then be used with confidence for checking the influence of potential subsequent events, such as modifications of topsides, new loadings or operating conditions.
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| Fig. 2. CLOV subsea spread. Subsea 7, the SURF contractor for Total, appointed BV for the certification subcontract. |
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Risk-based inspection. The model will form the basis for an ongoing risk-based inspection program and a BV asset integrity maintenance scheme. Powerful tools, such as the VeriSTAR HLC software, will focus inspection on relevant structural areas; prepare inspection campaigns by taking into account the means of access; assess the corrosion condition of the unit against BV’s or user-defined criteria; and manage data on the structure and topsides for the long term in an open format.
Subsea certification. BV certified the entire SURF installation. Subsea 7, the SURF contractor for Total, appointed BV for the certification subcontract, Fig. 3. A BV EPCI project team coordinated the design and installation engineering review, together with the necessary inspections in Europe for procurement, and in Angola for onshore construction in Lobito and offshore Angola. BV has previously certified the SURF for similar projects in Angola, such as Pazflor, built by Technip.
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| Fig. 3. FEM mapping of CLOV FPSO in as-built state. The model will form the basis for an ongoing risk-based inspection program and an asset integrity maintenance scheme. |
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Additional certifications. The certification activities included a full review of the engineering documentation to issue independent design review certificates (IRCs) for conformity to contractual specifications and standards. The scope of work includes the production rigid loops, water injection and gas export flowlines, umbilical and the riser system, based on three towers (two hybrid riser towers and one single hybrid riser).
For the procurement aspect, BV identified relevant intervention points for all vendor equipment, based on a risk-based approach. For the construction scope, BV inspectors in Angola witnessed the fabrication and assembly of the procured items in the yard at Lobito. This included the riser tower construction, suction piles, spools, pipe-in-pipe and double jointing activities, and various other subsea structures. Finally, BV surveyed each offshore installation phase.
Through the CLOV project, BV is pioneering a web-based geographic information system which groups, organizes and analyzes information from multiple sources and different formats. It presents all the information coherently, including engineering plans, site bathymetry and characteristics, and also the timeframe of operations and the position of units. The ability to access it, via the web, mirrors BV’s web-based AIMS system, which will help ensure cost-effective, risk-based inspection and maintenance throughout the life of the FPSO.
VALUE-ADDING SERVICES
The investment in independent monitoring, verification, classification and certification is relatively small, compared to the overall investment in the FPSO and associated systems. But that investment, in independent eyes watching everything, will pay back over the life of the field in smooth, trouble free production. 
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